I can tell you almost 100% that you do not have schizophrenia. I mentally Ill person has no idea that they are mentally ill. I of course dont have a degree (yet) im a 3rd year psych student though. I have had a simular experince though, normally i can smoke multiple bowls an hour. Then all of the sudden 6 months ago a few hits would get me blazed out of my mind. I started worrying and wondering why, and while driving I would think every car was a cop. (luggage racks) LOL. Anyways it got kinda bad for about a week i thought i was gonna have to give up smoking becuase of the paranoia. So actually i quit for 4 days, then tried again. But when i smoked i did it in my house in my room with some Bob and a couple of buddies. I didnt try getting stoned off my ass or anything like that. Just a nice relaxing puff and pass circle, and i didnt experince any paranoia. My tolerence was kinda screwey for the next 2-3 days then I was fine everything back to normal. If anything i would say your paranoia might be caused becuase your so worried about it. Next time you smoke do it with a couple buddies, try to relax as much as possible, maybe drink some calming tea or herbs. Light some relaxing incense and just try to make the whole experince as pleasent as possible and see what happens.